Method of processing bi-component acrylic fibers



United States Patent 3,251,113 METHOD OF PROCESSHNG BI-COMPONENT ACRYLHC FIBERS Coy .7. Gray and Walter R. Owens, Greenwood, S.C., as-

signors to Deering Milliken Research Corporation, Spartanburg, S.C., a corporation of Delaware No Drawing. Filed Feb. 10, 1961, Ser. No. 88,251

13 Claims. (Cl. 28-76) This invention relates to an improved method of processing textile fibers, and more particularly to an improved method of processing bi-component acrylic fibers in order to improve their ultimate bulking.

There is now commercially available in the textile field at least one bi-component acrylic fiber, Orlon Sayelle, which exhibits unique bulking characteristics. This bi-component acrylic fiber product, as shipped by the manufacturer, has two kinds of crimp present in the fiber. The first of these is a substantially minor mechanically produced crimp, similar to that in Orlon type 42 staple, and the second is latent in the fiber as a random spiral type of crimp. The purpose of the mechanical crimp is to provide the uecessarycohesion during processing. When the fiber is submitted to wet heat and subsequently dried, the random spiral crimp develops. The random spiral latent crimp results from the bi-component character of the fiber.

The present method of handling this bi-component acrylic fiber is to form the fibers as they are received from the manufacturer (if in staple form) (or after chopping, if in tow form) into a yarn, preferably of low twist, then to form the yarn into a fabric as by knitting, and thereafter subjecting the fabric to a wet heat treatment as by scouring, bleaching, and/or dyeing, after which the fabric is tumble dried. The wet heat treatment is carried out to develop the latent random spiral crimp in the yarn and this action together with the subsequent tumble drying causes the yarn in the fabric to achieve a desirable bulking. The yarn formed of this bi-component acrylic fiber may also be packaged-dyed or skein-dyed prior to forming into a fabric, in which case bulking takes place during yarn drying subsequent to Wet heat treatment. It has, however, previously been a distinct disadvantage that yarns made of Orlon Sayelle and which were packagedyed would not yield a commercially satisfactory degree of bulking, especially compared to the bulking of the same yarn which has been skein-dyed. It is most desirable, particularly from a production cost standpoint, to be able to package dye the yarn and still yield the quality, both in bulking and hand, of the conventionally treated skein-dyed yarns of this fiber.

An important feature of the present invention is the provision of an improved process for handling of such bi-component acrylic fibers, particularly Orlon Sayelle,

whereby the yarns formed therefrom will exhibit greater bulk and loftiness than has previously been achieved with yarns and fabrics formed of such fibers and processed in the conventional manner. .A particular feature is the improvement wherein package-dyed yarns formed of these fibers have greater bulk and loftiness than package-.

Sayelle, in such a manner as to reduce the temperature- 3,251,113 Patented May 17,1966

ICE

at which the bulking action of the yarn formed from' such fibers will take place.

Whereas it is the present and previous practice to form the desired yarn of these bi-component acrylic fibers form, with subsequent wet heat treatment for crimp developing being eflected after the yarn is formed, we have found that the ultimate crimp development and resultant yarn or fabric bulking are substantially increased by subjecting the Orlon Sayelle bi-cornponent acrylic fibers to a heat-setting treatment while they are in loose staple, sliver, tow, or roving form in a low external stress condition, preferably substantially zero tension and compression, and, prior to spinning into a yarn. The exact reasons for this notable improvement are not known; however, it is thought that such may result from the setting of the unrelieved latent crimp forces in such a manner as to make them more resistant to loss during the straightening action which is effected during Washing or other wet treatment of the fibers. In any event, the improvement in bulking is substantial, and is particularly noticeable in the case of package-dyed yarn formed of these fibers.

Referring in more detail to'our improved process, a mass of Orlon Sayelle bi-component acrylic fibers in staple form was carded in the conventional manner on a worsted carding frame, and the resulting sliver was subjected to a heat-setting treatment. This heat-setting treatment consisted of placing the sliver in a conventional pressure box and subjecting it to a vacuum for four minutes, then subjecting it to various temperatures with-j in the range of approximately 200 F. to a temperature approximately ten degrees below the sticking point of the fibers for two minutes by injection of pressurized steam into the box, then again to a vacuum for three minutes, then to a subsequent steam heat treatment Withinthe same temperature range for seven minutes, and again to a vacuum for five minutes. The preferred temperatures for heat-setting are from 225 to 280 F. Various combinations of vacuum and pressurized heating cycles. may be used, it being preferred, however, to use a full I Various heat-setting temperatures:

TAB LE 1 Heat-setting Skein Heat-setting cycle temperature, length, F. inches Full cycle (vac, heat, vac., heat, vac.) 277 13% Full cycle 252 14 Full cyele 227 14 Full cycle 204 15. 5 None (conventional) 17 As the temperature was increased the bulking, measured in terms of shrinkage, increased. To insure most advantageous heat treatment, it appears that the full heat cycle is most desirable. This is evidenced by the following further examples wherein a half-cycle (vacuum, heating, and vacuum) was employed in lieu of a full 6 cycle (vacuum, heating, vacuum, heating, vacuum) as in the above examples:

According to our invention, yarns formed of heat-set Orlon Sayelle maybe package-dyed and knit on a circular knitting machine at the same stitch setting as yarn formed of regular Orlon Sayelle (i.e., Orlon Sayelle fibers which have not been heat-set prior to forming into yarn), and the resulting bulking of the yarn in the knitted fabric after wet heat treatment is superior to that of the knitted fabrics formed of the conventionally processed Orlon Sayelle yarn. By way of example, 2/ count yarns of conventional non-heat-set Orlon Sayelle and, heat-set Orlon Sayelle (full heat-setting cycle at approximately 0 F.) were packaged-dyed and knit on a circular knitting machine at the same stitch setting. The sweater bodies were allowed to stand eight hours. The sweaters of heat-set Orlon Sayelle had begun to bulk during standing at room temperature of about 70 F., as evidenced by hand and shrinkage.

Some of the sweater bodies of each type were steamed and tumble-dried. The bodies of heat-set Orlon Sayelle bulked much more than the other sweaters. The remaining sweaters were scoured at 120 F., extracted, and tumble dried for 20 minutes at 200 F., which is the normal finishing procedure for knitted fabrics formed of Orlon Sayelle. The bodies of pre-heat-set Orlon Sayelle yarn had bulk considerably more than the conventional Orlon Sayelle sweaters. The following Table 3 shows the resultant lengths of the sweaters under these comparative conditions:

These same sweaters were then again washed and subjected to air drying in order to determine the recovery rate of the sweaters under air drying conditions. Both the sweaters of regular non-heat-set fibers and heat-set fibers recovered very slowly under these conditions, with no significant difference in the time required to reach their original dimensions. The following Table 4 shows the results for the variously process sweaters formed of the variously processed fibers:

more pleasing, wool-like hand both before this further washing and after the six weeks period, than the sweater bodies of Orlon Sayelle fibers which had been formed in the yarn in the conventional manner without a pre-yarn heat-setting The above examples illustrate that package-dyed yarns and fabrics formed of package-dyed yarns of pre-yarn heat-set package-dyed Orlon Sayelle bulk more and have a better hand than package-dyed conventionally processed Orlon Sayelle. 'Further comparative tests indicate that package-dyed yarns and knitted fabrics formed of package-dyed yarns of pre-yarn heat-set Orlon Sayelle even bulk more than skein-dyed yarns and fabrics formed of yarns of conventionally processed Orlon Sayelle fibers. This is particularly noteworthy in view of the fact that the previous standard of excellence of bulking for yarns formed of Orlon Sayelle fibers has been that of conventionally processed skein-dyed yarns. In these comparative yarn bulking tests the yarn formed of conventionally processed fibers was skein-dyed. The yarn formed of pre-yarn heat-set Orlon Sayelle fibers was package-dyed. The dyed. yarn samples were wound into skeins 26.5 inches long, secured and tumble dried. The following Table 5 shows the resulting ultimate skein lengths in inches, using 2/ 20 and 2/ 23 yarn count yarns, the pre-yarn heat-setting having been effected at approximately 250 F. for a full cycle as described previously, whereas the yarn of conventionally treated fibers received no prc-yarn heat-setting treatment:

This increased bulking of the yarn which has been formed of pre-yarn heat-set Orlon Sayelle fibersis also reflected in the fabrics knitted of this yarn. Sweaters were knitted on a flat knitting machine, employing the same stitch setting for three different yarns. One of the yarns was formed of Orlon Sayelle fibers which had been subjected to a pre-yarn full cycle steam heat-setting treatment at approximately 250, while another of the yarns was formed of conventionally processed Orlon Sayelle fibers (no pre-yarn heat-setting), and the third yarn was formed of 50% pre-yarn heat-set Orlon Sayelle fibers and 50% conventionally process Orlon Sayelle fibers. The 100% heat-set fiber yarn and the 50% heat-set fiber yarn was package-dyed, whereas the yarn formed of conventionally processed Orlon Sayelle fibers was skein-dyed, prior to knitting. In the following Tables 6 and 7 are shown the resultant sweater dimensions and weights after TABLE 4 Sweater length, inches I After Pre-yarn fiber heat-setting Finish treatment 6 wks.

Before After After wash 16 hrs. 28 hrs.

Steam, tumble dry 23. 5 26. 0 25. 5 23. 5 Wash, tumble dry 21. 5 23. 5 23. 5 22.0 None. Wash, tumble dry, steann. 21. 25 23.0 22. 25 21. 0 Heat-set, full eyclc, 250 F Steam, tumble dry 20. 24. 5 23.0 21. 0 Heat-set, full cycle, 250 F Wash, tumble dry 18. 5 22. 5 21.0 19. 0 Heat-set, full cycle, 250 F Wash, tumble dry, steam 19. 0 21.0 20.0 18. 5

In each case the sweater bodies of pre-yarn heat-set Orlon Sayelle fibers, in addition to bulking more, had a tumble drying (Table 6) and after subsequent steaming (Table 7):

TABLE 6.SWEATER MEASUREMENTS AFTER WASHING of both garments was same due to the offset of AND TUMBLE DRYING creased bulking and consequent piece size shrinking versus originally finer yarn count of the pre-yarn heat-set fabric, Fiber and y treatment L s ,Y f s the sweater of conventionally processed Orlon Sayelle es es fibers would have required substantially more yarn in Pre am heat at aeka e order even to approach the improved hand and appearance ai 2/20 15.5 3,375 m of the garment formed of fibers processed according to z 7i l a ,P 16 5 34 75 7 our invention. This yields obvious and important adc i fifigj'i551 5 vantages from both production cost and sales appeal heat-SetLSkem-dYed 2/20 17-25 10 viewpoints. The results of these comparative tests are shown in the -following Table 8:

TABLE 8 Piece dimensions after dyeing and tumble drying Finished Fiber and yarn treatment Yarn Piece sweater wt.,

- count wt., lb./d0z. lbJdoz.

Length, Width, Cufi, inches inches inches Pre-yarn heat-set 2/23 21 36V 2V x 23 11 8V Conventional 2/20 24% 38%: 2 Zx2s A 8% TABLE 7.SWEATER MEASUREMENTS AFTER WASHING, TUMBLE DRYING, AND SUBSEQUENT STEAMING As a further example of the merit of this invention, a package-dyed 2/23 count yarn formed of pre-yarn heat-set Orlon Sayelle fibers was knitted into a sweater, and a sweater was also knitted of 2/20 count yarn of 'skein-dyed, conventionally processed Orlon Sayelle fibers.

The sweater of package-dyed 2/23 count yarn had a comparable hand and quality to that of the skein-dyed sweater of -2/20 yarn count, and weighed 8% less than the sweater of skein-dyed conventionally processed Orlon Sayelle fibers.-

As an example of the improved qualities of piecedyed fabrics'made of yarn having Orlon Sayelle fibers processed according to this invention, two comparative sweaters were made. Orlon Sayelle in tow form was converted into sliver on a Pacific Converter. Part of the sliver was full cycle heat-set at approximately 250 F. according to the invention, and was formed into 2/23 count yarn. while the remaining sliver was formed into 2/2() count yarn in the conventional manner without pre-yarn heat-setting of the fibers. One sweater was made of the 2/23 count yarn formed of rundyed pre-yarn heat-set Orlon Sayelle fibers according to the invention, and another sweater was made of the 2/20 count undyed yarn formed of conventionally processed Orlon Sayelle fibers. In each case the yarn was knitted with the same stitch setting and original piece size. The knitted pieces of both types of yarn were then dyed and tumble dried, weighed, and measured. The pre-yarn heat-set pieces were substantially more bulky after dyeing and drying than the conventional yarn pieces, and this was reflected in a marked difference in dried tfabric piece dimensions. The respective pieces were then cut and formed into two sweaters of identical size, which were weighed and compared for bulk, appearance and hand. The sweater garment from pre-yarn heat-set fibers was visibly much more bulky and had a more pleasing hand and appearance than the garment made 'from yarn formed of conventionally processed Orlon Sayelle fibers. Although the final weight While several examples of the invention have been described, it will be apparent to those skilled in the art that various modifications and improvements may be made without departing from the scope and spirit of the invention. For instance, while the pre-yarn heatsetting treatment has been illustrated as being carried out on sliver, such may also be etfected while the yarn is in loose bulk staple, tow, or roving form, the major criteria being that of applying the heat-setting treatment of the fibers while the fibers are in a state of, low external stress prior to yarn formation. Also, while the heatsetting treatment is illustrated as having been applied by subjecting the yarn to a steam environment, it will be appreciated that such may also be eifected by subjecting the yarn to a dry heat within the desired temperature range of approximately 200 F. to a temperature approximately 10 below the sticking point of the bi-component acrylic fibers. Accordingly, it is. to be under stood that the invention is not tobe limited by the illustrative examples, but only by the scope of the appended claims.

That which is claimed is:

1. The method comprising heat-setting a mass of bicomponent acrylic fibers, both components of which are acrylic in nature, said fibers having unrelieved latent crimp stresses therein whereby said fibers tend to straighten when wet and to crimp upon drying, said heat-setting being conducted while said fibers are in a low external stress condition and prior to spinning of the fibers into yarn, thereafter spinning said fibers into yarn, forming a fabric :from said yarn, subjecting said fabric to a wet heat treatment and drying said fabric to substantially develop the crimp in said fibers as they lie in situ in said fabric, said heat-setting comprising subjecting the fibers to a vacuum, then to a heat-setting treatment, then to a vacuum, then to a heat-setting treatment, and then to a vacuum.

'2. The method according to claim '1 wherein said yarn is formed into a knitted fabric.

3. The method according to claim 2 wherein said wet heat treatment is efiected by dyeing of said fibers in situ in said yarn and knitted fabric.

4. The method of claim 1 wherein the yarn is tumble dried after said wet-heat treatment and then steamedafter said tumble drying.

5. The process of claim 1, wherein the wet heat treatment comprises washing, tumble-drying and steaming.

6. A method of forming fabrics having high bulk characteristics comprising i (1) providing a mass of bi-component acrylic fibers having unrelieved latent spiral crimp stresses therein whereby said fibers tend to straighten when wet and to crimp upon drying;

(2) subjecting said fibers to a heat-setting procedure comprising, in series, a vaeuum-steaming-vacuumsteaming-vacuum cycle, said steaming being conducted at temperatures between the limits of approximately 225280 F., said heat-setting being conducted while said fibers are in loose, substantially untensioned staple form;

(3) spinning said heat-set fibers into yarn;

(4) subjecting said yarn to a wet heat treatment comprising the hot liquid dyeing of said yarn;

(5) drying said yarn to substantially devolp the crimp in said fibers in the yarn;

(6) knitting said yarn into a fabric;

(7) exposing said fabric to a wet heat treatment comprising scouring of said fabric;

(8) and then tumble-drying said fabric, whereupon a higher degree of crimp in the fibers is obtained than when said fabric is similarly produced and treated except that the heat-setting treatment prior to yarn formation is eliminated.

7. The method comprising providing a mass of bi-component acrylic fibers, both components of which are acrylic in nature, said fibers having unrelieved latent crimp stresses therein whereby said fibers tend to straighten when wet and to crimp upon subsequent drying; subjecting said fibers, prior to spinning into yarn, to a vacuum, then to a heat-setting treatment, and then to a vacuum, said fibers being in loose, substantially untensioned condition during said heat-setting treatment, subjecting said fibers to a wet heat treatment and drying said fibers under relaxed conditions to induce a high level of crimp in said fibers.

8. The method according to claim 7 wherein said heatsetting treatment is effected by subjecting said mass of fibers to a temperature between the limits of approximately 200 F. and a temperature approximately 10 below the sticking point of said fibers.

9. The method according to claim 7 wherein said heatsetting treatment is effected 'by subjecting said mass of fibers to steam.

10. The method according to claim 7 wherein said mass is subjected to two heat-setting treatments prior to spinning of said fibers, said heat-setting treatments comprising subjecting said fibers to a vacuum, then to a heatsetting treatment, then to a vacuum, then to a heat-setting treatment, and then to a vacuum.

11. The method according to claim 7 wherein said wet heat treatment is effected by hot liquid dyeing of said fibers in situ in the yarn.

12. The process of claim 7, wherein the fibers are skein dyed after the heat-setting treatment and prior to spinning into yarn.

13. The process of claim 7, wherein the fibers are spun into yarn and dyed prior to production of a garment.

References Cited by the Examiner UNITED STATES PATENTS 2,439,815 4/1948 Sisson 2882 2,931,091 4/1960 Breen 2882 3,038,240 6/1962 Kovarik 2872 OTHER REFERENCES Du Pont Textile Fibers, NP-11, May 1960, article entitled, Orlon Sayelle Acrylic Fiber, 19 pages, Du Pont Orlon Technical Fiber Manual.

DONALD W. PARKER, Primary Examiner.

RUSSELL C. MADER, MELVIN STEIN, Examiners. 

1. THE METHOD COMPRISING HEAT-SETTING A MASS OF BICOMPONENT ACRYLIC FIBERS, BOTH COMPONENTS OF WHICH ARE ACRYLIC IN NATURE, SAID FIBERS HAVING UNRELIEVED LATENT CRIMP STRESSES THEREIN WHEREBY SAID FIBERS TEND TO STRAIGHTEN WHEN WET AND TO CRIMP UPON DRYING, SAID HEAT-SETTING BEING CONDUCTED WHILE SAID FIBERS ARE IN A LOW EXTERNAL STRESS CONDITION AND PRIOR TO SPINNING OF THE FIBERS INTO YARN, THEREAFTER SPINNING SAID FIBERS INTO YARN, FORMING A FABRIC FROM SAID YARN, SUBJECTING SAID FABRIC TO A WET HEAT TREATMENT AND DRYING SAID FABRIC TO SUBSTANTIALLY DEVELOP THE CRIMP IN SAID FIBERS AS THEY LIE IN SITU IN SAID FABRIC, SAID HEAT-SETTING COMPRISING SUBJECTING THE FIBERS TO A VACUUM, THEN TO A HEAT-SETTING TREATMENT, THEN TO A VACUUM, THEN TO A HEAT-SETTING TREATMENT, AND THEN TO A VACUUM. 